1. Field of the Invention
The present invention relates to a single reel-type tape cartridge where a single tape reel, on which a magnetic tape is wound, is rotatably held in a case main body.
2. Description of the Related Art
A magnetic tape cartridge disclosed by Japanese Laid-Open Patent Publication No. 2000-260156 is known as one example of this kind of tape cartridge. This magnetic tape cartridge is a single reel-type cartridge recording medium, and is constructed of a cartridge case and a reel around which a magnetic tape is wound. In this case, a cylindrical leader pin for withdrawing the magnetic tape from the cartridge case is fixed to an end of the magnetic tape.
The cartridge case is constructed by fitting together an upper case and a lower case and encloses the reel in a rotatable state. In this case, cutaway parts that compose an opening for withdrawing the magnetic tape are respectively formed in the side surfaces of the upper case and the lower case. In the vicinity of the opening in the upper case and the lower case, storage parts for storing fixed parts formed at both ends of a leader pin are formed. Also, in a vicinity of the opening in the cartridge case, there is provided a locking member that regulates the movement of the leader pin by having end engaging parts thereof contact (or be close to) the fixed parts.
In this magnetic tape cartridge, in a state where the magnetic tape is wound on the reel (the “unused state”), the fixed parts of the leader pin that is fixed to the end of the magnetic tape are respectively stored in the storage parts and the end engaging parts of the locking member contact the fixed parts. In this way, movement of the leader pin is regulated.
On the other hand, when the magnetic tape cartridge has been loaded in a recording/reproducing apparatus, for example, a tape withdrawing member of the recording/reproducing apparatus engages the leader pin and withdraws the leader pin from the opening in the cartridge case. At this time, while the fixed parts of the leader pin push back the end engaging parts of the locking member against the pressing force of the end engaging parts (i.e., against the elastic force of the locking member), the fixed parts are pulled out of the storage parts against friction caused by side surfaces of the fixed parts sliding against contact surfaces of the end engaging parts. Next, a reel in the recording/reproducing apparatus starts to wind the magnetic tape and recording or reproduction of data is carried out by a recording/reproducing unit of the recording/reproducing apparatus. After this, when recording or reproduction has ended, the recording/reproducing apparatus rotates the reel of the magnetic tape cartridge to rewind the magnetic tape. Next, when the rewinding of the magnetic tape is almost complete, the rewinding of the magnetic tape causes the fixed parts of the leader pin to push back against the pressing force of the end engaging parts of the locking member and the fixed parts are pulled back into the storage parts against friction caused by the side surfaces of the fixed parts sliding against the contact surfaces of the end engaging parts. After this, the fixed parts are stored in the storage parts and the end engaging parts contact the fixed parts. In this way, the movement of the leader pin is regulated.
However, by investigating the tape cartridge described above, the present inventors discovered the following problem. That is, in tape cartridges including the conventional tape cartridge described above, as shown in FIGS. 20 and 21, contact surfaces 82 of engaging parts (end engaging parts) of a spring member (locking member) 81 are normally formed as flat surfaces (i.e., surfaces that are straight in the up-down direction). In this case, when the leader pin 83 is withdrawn and pulled back in, there is surface contact or linear contact between the contact surfaces 82 of the spring member 81 and the end parts (fixed parts) 84 of the leader pin 83. Also, to make it possible for the leader pin 83 to move smoothly in this type of tape cartridge, the length of the leader pin 83 is set slightly shorter than the distance of separation between the upper case (not shown) and the lower case 86. This means that as shown in FIGS. 20 and 21, when the tape is wound out and rewound, the leader pin 83 moves up and down by an amount equal to the above difference in lengths, so that the contact surface area or contact length between the contact surfaces 82 of the spring member 81 and the side surfaces 85 of the end parts 84 of the leader pin 83 fluctuates and the contact positions between the surfaces 82 and 85 vary. Accordingly, in a conventional tape cartridge, due to fluctuations in the contact surface area or contact length between the contact surfaces 82 and the side surfaces 85 and the variation in the contact positions, the friction due to the sliding of both surfaces, for example, fluctuates, so that in reality the force (hereinafter also referred to as the “attaching/detaching force”) required to withdraw and pull back in the leader pin 83 against the pressing force and friction described above also fluctuates, which causes other problems.
More specifically, for this kind of tape cartridge, to stabilize the operation when the recording/reproducing apparatus withdraws and pulls back in the leader pin 83, for example, upper and lower limits are set for the attaching/detaching force. This means that when the spring member 81 for this kind of tape cartridge is designed, the upper and lower limits (tolerance) for the pressing force of the spring member 81 are set (calculated) based on the upper and lower limits of the attaching/detaching force. However, in a conventional tape cartridge, due to the fluctuations in the attaching/detaching force caused by factors such as the fluctuations in the contact surface area or contact length between the contact surfaces 82 and the side surfaces 85 and the variation in the contact positions during use, it is necessary to set the tolerance for the pressing force at a small value in anticipation of fluctuation in the attaching/detaching force. Accordingly, in a conventional tape cartridge, it is necessary to machine the spring member 81 with a higher precision corresponding to how small the tolerance of the pressing force is, so that there is the problem of a high manufacturing cost for the spring member 81 and in turn a high manufacturing cost for the tape cartridge.